PIC Microcontroller ADC Conversion Program

PIC Microcontroller ADC Conversion Program Knowledge Points

1. Introduction to PIC Microcontroller and Application Scenarios

• PIC (Peripheral Interface Controller) Microcontroller: A widely used microcontroller in embedded systems, known for its small size, low power consumption, and high cost-effectiveness. It has broad applications in industrial control, consumer electronics, and more.
• Analog-to-Digital Conversion (ADC): The process of converting an analog signal to a digital one. In many cases, the information obtained from sensors is in analog form, while microcontrollers only process digital signals. Therefore, ADC is necessary to convert these signals.

2. Choice of Programming Language

• Assembly Language: Suitable for applications with high performance requirements but with complex code and low maintainability.
• C Language: Compared to assembly, C is easier to read and write, improving development efficiency. This program is written in C.

3. Key Code Analysis

1. Configuration Initialization

__CONFIG(0x1832);  // Set chip configuration, value must be adjusted based on actual requirements

• Configuration Word: Used to set the microcontroller's basic parameters, such as clock frequency and power management. The value 0x1832 indicates the selection of a 4MHz clock.

2. Constant Definition

const char TABLE[] = {0xc0, 0xf9, 0xa4, 0xb0, 0x99, 0x92, 0x82, 0xf8, 0x80, 0x90};

• TABLE Array: Stores the display codes for digits 0-9, making it easier for subsequent LED display operations.

3. Main Function Implementation

void main() {
   int result = 0x00;  // Initialize ADC conversion result
   while (1) {  // Infinite loop to keep the program running
       int i;
       result = 0x00;
       for (i = 5; i > 0; i--) {  // Perform 5 ADC conversions to take the average
           init();  // Initialize ADC
           ADGO = 0x1;  // Start conversion
           while (ADGO);  // Wait for conversion to finish
           result += ADRESL;  // Accumulate each conversion result
       }
       result /= 5;  // Take the average
       display(result);  // Display the conversion result
   }
}

• Loop Structure: An infinite while loop is used to continuously execute the program.
• Multiple Samples for Average: The program uses five samples to calculate the average value, reducing noise interference.

4. Initialization Function

void init() {
   PORTA = 0xFF;
   PORTD = 0xFF;  // Clear display
   TRISA = 0x1;  // Set RA0 as input mode
   TRISD = 0x00;  // Set all PD ports as output
   ADCON1 = 0x8E;  // Set ADC channel to RA0 and choose analog input mode
   ADCON0 = 0x41;  // Set ADC conversion rate to Fosc/8, choose RA0 as ADC channel
   DELAY();  // Delay to ensure ADC stability
}

• Port Configuration: Set up port modes using TRISA and TRISD registers.
• ADC Configuration: Set ADC parameters using ADCON1 and ADCON0 registers.
• Delay Function: Ensures the ADC has enough time to stabilize.

5. Display Function

void display(int x) {
   int bai, shi, ge, temp;
   temp = x;
   bai = temp / 0x64;  // Hundreds place
   shi = (temp % 0x64) / 0xA;  // Tens place
   ge = (temp % 0x64) % 0xA;  // Ones place
   PORTD = TABLE[bai];
   PORTA = 0x37;  // Control hundreds place display
   DELAY();
   PORTD = TABLE[shi];
   PORTA = 0x2F;  // Control tens place display
   DELAY();
   PORTD = TABLE[ge];
   PORTA = 0x1F;  // Control ones place display
   DELAY();
}

• Digit Display: The result is split into hundreds, tens, and ones places, then displayed on an LED display.

6. Delay Function

void DELAY() {
   int i;
   for (i = 0x100; i--;);  // Simple delay function
}

• Loop Count: A loop is used for delay to provide sufficient wait time during program execution.

4. Conclusion

This program implements ADC conversion on a PIC microcontroller, using the average of multiple samples to improve accuracy. The results are displayed on LEDs for easy visualization of the analog signal value. The program structure is clear and logical, making it an excellent example for learning embedded system development.